President Barack Obama returned to the United States after a trip to Latin America that included a stop in Argentina and a historic visit to Cuba where he met with President Raul Castro.

Obama, his wife, two daughters and mother-in-law took off on Air Force One from Buenos Aires Ezeiza International Airport and landed at Joint Base Andrews outside Washington early Friday. They returned to the White House to begin preparations for the holiday weekend, including the famous Easter egg roll.

Obama said the United States was slow to speak out on the atrocities committed during Argentina's former dictatorship but that his administration will "confront the past with honesty and transparency."

"What happened here in Argentina is not unique to Argentina and it’s not confined to that past," said Obama in Buenos Aires. "Each of us have a responsibility each and every day to make sure that wherever we see injustice, wherever we see rule of law flouted that we are honest witnesses, that we are speaking out, that we are examining our own hearts and taking responsibility to make this a better place for our children and our grandchildren."

Obama on Thursday visited a memorial park to victims of the so-called "Dirty War" on the 40th anniversary of the coup that installed a brutal military regime.

The president said it takes courage for a society to address "uncomfortable" truths about the "darker parts of its past."

"Confronting crimes committed by our own leaders, by our own people, that can be divisive and frustrating. But it’s essential to moving forward to building a peaceful and prosperous future in a country that respects the rights of all of its citizens," Obama said.

Declassified U.S. documents have shown that the United States backed the regime that human rights activists say was responsible for the death or disappearance of some 30,000 people between 1976 and 1983 - the Dirty War period.

Obama has said his administration will try to make amends by declassifying more documents which made further detail the role the United States played in the dictatorship.

President Barack Obama watches as Argentine President Mauricio Macri tosses roses into the river during their visit to Parque de la Memoria (Remembrance Park) in Buenos Aires, Argentina, March 24, 2016.

Criticized for visiting on coup anniversary

Critics of the president's visit, including many who lost friends or relatives during the years under the military government, say the Obamas should not have come to Argentina on such an important anniversary. Protests linked to the anniversary were held in Buenos Aires and across the nation.

Obama was the guest of Argentina's new president, Mauricio Macri, who is intent on strengthening the strained ties between the two nations.

After being guests of honor at a state dinner Wednesday night, President Obama and first lady Michelle Obama attended a ceremony Thursday to remember the victims of the regime at Remembrance Park in Buenos Aires.

Evidence of U.S. support for South American dictatorships has been public knowledge for more than a decade; but, the United States announced last week, at the behest of the Argentine government, that it will declassify even more military and intelligence documents linked to the Dirty War.

White House aide Ben Rhodes said last week that the president believes "moving forward in the Americas or any other part of the world involves a clear-eyed recognition of the past."

President Barack Obama, right, and first lady Michelle arrive for a state dinner with Cuba's President Raul Castro, left, at the Palace of the Revolution in Havana, March 21, 2016.

Landmark Cuba visit

The president's trip to Argentina followed a landmark visit to Cuba, the first by a sitting U.S. president in almost nine decades. During his meeting with President Castro, Obama called on the U.S. Congress to lift the decades-long trade embargo on Cuba.

Macri said Wednesday that the Obamas' visit came "at a perfect time" because, he said, "Argentines have understood and decided to build mature and reasonable relationships with every country in the world."